Grinding wheel and method of balancing the same



Feb. 0, 19371 C, J HUDSON 2,070,360

GRINDING WHEEL AND METHOD OF BALANCING THE SAME Filed Dec. 9, 1956 1 MEUD 0F Gharles ll. Hun, est ylstcn, a, as-

signor to Norton Comp, 'gorcester,

a corporation of Application ember 9, 1936, fierial No. llt,993

The invention "relates to grinding wheels and a method of balancing them.

One object of the invention is to provide an improved method for balancing grinding wheels particularly those bonded with ceramic bond which are relatively dense, and dense wheels of arrangements of parts, and in the several steps and relation and order of each ofsaid steps to one or more of the others thereof, all as will be illustratively described herein, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawing in which is illustrated one of many possible embodiments of the mechanical features of this invention,

Figure 1 is an edge elevation of a grinding wheel together with an apparatus for determining the out of balance condition;

Figure 2 is a side'elevation of the apparatus of Figure l;

Figure 3 is a perspective view of weights used to determine the amount of out of balance;

Figure 4 is a plan view oi. a grinding wheel together with a dam which may be used in carrying out the method of the invention;

Figure 5 is an enlarged cross-sectional view of one'of the parts of the dam'of Figure 3, being a sectional view on the line 5-5 of Figure 3;

Figure 6 is a magnified sectional view of abrasive grains secured together with bond and having thereon a deposit of the balancing material, in order to illustrate the manner in which the balancing material is incorporated into the grinding wheel.

I provide a grinding wheel. The invention can be carried out with many different types of grinding wheels but is particularly applicable to be embodied in or practiced in connection with any one of the reasonably dense wheels, such as phenolic or plyptal resin wheels, dense ceramic or silicate wheels, and cement wheels. Furthermore dirty or greasy wheels of any type are more easily balanced according to the present method.

The balancing of large diameter vitrified grinding wheels, especially those used for crankshaft grinding and the like, has long been a special problem. In the past the balancing achieved has been in some cases nearly perfect but in other cases far from perfect. Moreover, a wheel which is in static balance is not necessarily in dynamic balance and furthermore a wheel which is in dynamic balance at one diameter may be out of balance when it is reduced in diameter owin to ordinary wear. Some grinding wheels come from the kiln almost in perfect balance but this is amatter of accident as there is a certain amount of variation in density under present manufacturing conditions which results in an out of balance condition for a newly manufactured wheel in most cases, even though geometrically the wheel is a perfect cylindrical disk with a central hole axially located.

Referring first to Figures 1 and 2,1 provide a balance determiningfixture comprising an arbor it upon which is mounted a wheel holder it having a hub i3 secured to the arbor ii and a drum it which fits the internal hole it of the grinding wheel with a close sliding fit. I further provide a, pair of tracks 86, i6 which are horizontally spaced apart and may be shaped substantially as shown.

The arbor ii is now placed upon the tracks it, IS with the wheel It between them as shown in Figures 1 and 2. The wheel in will come to rest with the heavy side thereof down.

Referring now to Figure '3, I provide a spring clip l'l which may be shaped as therein shown and which has a known weight, for example a unit weight of one ounce. I provide a number of pins l8 also of known weight. Placing a mark at the top of the wheel after it comes to rest, I place the clip ill just to the right or left of this mark with the coiled portion l9 thereof extending across the periphery of the wheel as shown in Figure 2. I now add and subtract, weights it until the wheel will come to rest in any position with the added weights between a position just over the wheel axis and on the same level as the wheel axis. That is to say, if I draw a diameter line starting at the mean or average position of the added weights, the wheel should come to rest when this diameter line is horizontal andat various inclinations of this diameter line between the horizontal and the vertical. I use the two top quadrants in moving the weights as otherwise the weights i8 will not stay in position.

From the number of weights I now know that the wheel is out of balance by a given amount.

I now place the wheel, duly marked at the point i 20 by means of a pair of long bars 2|, an intermediate sized bar 22 and a small bar 23. These bars, except for their length, are identical and in cross section as shown in Figure 5 are rectangular and have a piece of sponge rubber 24 secured to their finely divided comminuted material, for example of the order of 600 mesh grain size or finer. Examples of comminuted materials which may be used are alumina and silicon carbide. I may also use finely divided copper or finely divided iron. In fact, any substance which may be provided in finely divided, comminuted form and which is, at normal temperatures, a solid may be used. However, I prefer substances with high specific gravities to substanceswith low specific gravities. I prefer substances which are insoluble in water. I also prefer substances which will not in any way afiect the grinding properties of the wheel or that portion of the wheel to which they may be added. I also prefer to use a substance which is undetectable or difiicultly detectable in the wheel as otherwise sales resistance in selling the wheel may be encountered although in fact the wheel be not at all affected. Another point to be mentioned is that it is desirable that the substance be not poisonous to the workman who is using it to balance wheels. The examples given have all the qualities desired and substantially no badfeatures. However, it may be mentioned that it is well tobalance white wheels with a white substance, wherefore the white variety of alumina may be used, and on the other hand to balance red wheels with a red substance, in which case finely divided copper may be advantageously used, and for the same reason it is well to balance dark gray or black wheels witha black substance wherefore silicon carbide may be preferred. Alumina and silicon carbide may be obtained in very finely divided form but it is somewhat more difficult to obtain powdered metals much more finely divided than 200 or 250 mesh size. The method of the invention accordingly has particu-, lar features in connection with the use of balancing substances which cannot readily be obtained in very finely divided form where they may be preferred because of their particular color, as in the case of copper in the above example.

I select a quantity of the balancing or compensating material which, when introduced into the wheel uniformly in the area defined by the dam 20, will exert a couple equal to the couple exerted by the weights l1 and I8 which actually compensated for the out of balance condition. What weight of material will exert this couple is determinable by mathematics. Forexample, if the wheel is a disk without a central hole and the dam is constructed to define a true sector (which is a condition which can be approximated), the weight of the compensating, balancing material should be to the weight of the weights I1 and I 8 as fifty-five is to thirty-eight and one-half.

Having thus set aside the proper weight of balancing material which shall compensate for the out of balance condition of the wheel, I mix it with enough water to make a slip or slurry. To

the water I add a suitable quantity of a wetting out agent. This may be done either before or after the balancing material is added; it makes no difference.

There are many substances which act as a wetting out agent with respect to water, to give the water greater effective fluidity. The characteristic which is desired is the property of penetra tion into the wheel. This is a phenomenon akin to capillarity and sometimes described as a matter of relative surfacetension. There may also be other factors involved but if the particular liquid has imparted to it the property 'of increased attraction to the solid, the increase of such attraction being greater than the increase, if any, in

the surface tension of the liquid itself, it will act as a wetting out agent. Whether this statement of the physics involved is a correct theory or not,

there are a great class of substances which act ef-' Various new soaps or substitutes for soap have recently been proposed; such as sodium lauryl sulphate, sodium octadecyl sulphate, sodium oleyl sulphate, Igepon A and Igepon T. Any of these may be used. Another example is the product sold under the trade name Alkanol B which has been found very effective as a wetting out agent. I may use sodium silicate.

The slip or slurry with the wetting out agent is then poured inside the dam 20. The material should then be worked with the fingers until the comminuted material penetrates the wheel. When the material has penetrated the wheel, the operator removes the dam and washes the wheel with a sponge and clear water. This is for the purpose of removing the discoloration caused by the material which remained on the surface.

The dam 20 may be dispensed with entirely under conditions of practical operation. It is described herein as it is a refinement which may be used when the most accurate results are wanted and especially where the very dense wheels are involved, For most wheels entirely practical and commercial results may be achieved by simply pouring the slurry onto the light side of the wheel and working it in with the fingers.

The wetting out agent has the property of carrying the compensating material into the wheel in cases where it will not otherwise go in. Probably there is a double action involved. The water is not only attracted by the grain and bond of the wheel, whether this be organic bond or vitrified bond and whatever type of grain, but it also holds .on to the compensating material more tenaciously by reason of its increased attraction for such. At least I have found that excellent results are achieved'in actual practice, whatever the reason therefor. The water seems to hold on to the comminuted material actually better than without the use of the wetting out agent.

Although the water or other liquid will dry out in the course of time if nothing is done to the wheel, nevertheless I prefer to dry the wheel in a drying chamber, using a temperature in the order of F. The wheel is in balance when it is dry. The wetting out agent probably leaves stances and, indeed. no measuring thereof appears to be important. A little amount will do some good and probably there is an upper limit wheremorewill not add to the results. In practice I use about one ounce to aquart of water when using 'Alkanol B, but this is not to be regarded as a critical limit or anything in the nature thereof.

The pulverulent balancing material goes into the pores of the wheel but does not fill them. A cross section of that portion of the wheel which was balanced is shown in Figure 6 where in the abrasive grains are designated by the numeral 25, bond by numeral 26 and balancing material by numeral 21.

It will thus be seen that there has been provided by this invention a method in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that which consists in introducing into the pores of the wheel, on the light side of its axis, a sumcient quantity of pulverized mineral material in a vehicle of water with a wetting out agent to make the weight of the light side substantially equal to the weight of the heavy side, the presence of such material not altering the grinding properties of the wheel.

2. The method of balancing an abrasive wheel, which consists in introducing into the pores of the wheel, on the light side of its axis, a sumcient quantity of pulverized "mineral compound in a vehicle of water with a wetting out agent to make the weight of the light side substantially equal to the weight of the heavy side, the presence of such material not altering the grinding properof water with a wetting out agent to make the weight of the light side substantially equal the weight of the heavy side, the presence oi said substance not altering the grinding properties of the wheel.

CHARLES J. 

